


What A CATastrophe

by Tesvyn



Series: The One-Shot March Challenge [13]
Category: Doctor Who, Harry Potter - J. K. Rowling
Genre: Animal Instincts, Animal Traits, Cheetah Virus (Doctor Who), Cross-Posted on FanFiction.Net, Fobwatched Time Lord, Forehead Kisses, Friendship, Fur, Harry Potter is The Master (Doctor Who), Hermione Granger is The Doctor's Companion (Doctor Who), Hermione Granger is a Good Friend, Medical Procedures, Minor The Doctor/The Master (Doctor Who), One Shot, Ron Weasley is a Good Friend, Soft Doctor (Doctor Who), Supernatural Illnesses, Triwizard Tournament
Language: English
Status: Completed
Published: 2021-03-13
Updated: 2021-03-13
Packaged: 2021-03-22 06:22:04
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,004
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30034407
Author URL: https://archiveofourown.org/users/Tesvyn/pseuds/Tesvyn
Summary: The stress of the TriWizard Tournament brings about some unpleasant changes to Harry.
Series: The One-Shot March Challenge [13]
Series URL: https://archiveofourown.org/series/2187630
Comments: 1
Kudos: 38





	What A CATastrophe

When Harry stalked, quite literally, out of the dorm room and into the common room the day before the second task in the Triwizard Tournament, no-one was surprised by just how stressed the boy appeared. There were dark bags under his eyes, and he looked just about ready to snap at anyone who spoke to him.

Hermione put the book she was reading down onto the armrest of the chair she was sat on and looked at him in concern, "Harry, are you alright?"

His shoulders tensed and he looked over at her, "I'm fine," he hissed, a fang slipping past his lip.

Hermione frowned and stood up as he drew his lip back over the sharpened canine, looking somewhat panicked.

"Harry..." she trailed off, slowly walking over to him.

He looked around the room, trying to avoid eye contact with her as she grew closer.

Eventually, she placed her hand on his shoulder, and he reluctantly turned his head to look at her.

They stood there staring at each other in silence for a moment, before Hermione bought her other hand up to his face, pulling his lips back and revealing long sharp canines on both his bottom set and top set, the rest of his teeth sharper than a human's but still the same size as regular incisors, premolars, and molars.

Honestly, it reminded her of Crookshank's teeth, very catlike, and she had to wonder...

"Harry, are you..." she turned to look around the room, quickly casting a privacy spell, then continuing her questioning, "are you learning to become an Animagus?"

He looked shocked, but frowned at her, "no," he admitted, "I woke up like this."

"A prank?"

He shrugged, "maybe."

She frowned at his seemingly casual acceptance of the matter but figured he was likely too stressed by the Tournament to really care about a prank that was rather harmless in the long run.

She sighed, "well, if it causes you any issues, or it's not gone by the end of the week..."

"Go to Madame Pomfrey, I know."

She nodded at him seriously, "I suppose it's time for breakfast then, Ron looks like he's about to come over and drag us there by force."

Harry turned to look behind him at the ginger-haired boy and decided that he did indeed look like he would do that.

He snorted, "it might be in our best interests, yeah."

_**What A CATastrophe** _

The day after the second task had happened, Harry slumped down in the chair next to Hermione in the common room, hands gripping the arms tightly.

"What's wrong?" she asked him.

He stared into the fire, and Hermione heard the sound of something scraping across wood, she looked down at where his hands were gripping the arms and realised that his fingernails were a lot sharper and were leaving scratches in the wood.

"Nothing."

She looked up from where she had been examining his... claws and frowned.

"This isn't 'nothing', Harry."

"I don't know what to tell you, Hermione," he whispered, bringing his hands up to his lap, where he began fiddling with the claws that now adorned his hands, "I don't know what's happening."

They sat there, the sounds of the fireplace crackling and the other students chattering filling their silence.

"It could still be a prank," she offered him, "a multi-layered one, activated bit by bit."

He looked at her from the corner of his eye, "yeah?"

She smiled and pulled him into a hug over the arms of their chairs, "if it's not, we can always figure out what's wrong and fix it.

A small smile graced his face, "of course."

_**What A CATastrophe** _

A week passed and nothing else happened to him, but the teeth and claws did not change back, and so Hermione and Ron both ushered him into the Hospital Wing.

Madame Pomfrey was on him as soon as he stepped foot into the room, "Mr Potter, back again already?"

He looked at the floor in embarrassment, and Hermione realising that he wasn't going to explain his situation, raised her hand and moved his lips out of the way, exposing his teeth. Once she was certain that she'd seen his teeth, she removed her hand and pulled one of his up for inspection.

"I see," the woman hummed, then looked at the boy, "right you, get onto that bed and I'll be with you in a moment."

Harry sighed and did as he was told, slipping his shoes off of his feet before he stepped up onto the bed, picking at his claws once he was sat there, Hermione and Ron sat on the two visitors chairs next to the bed.

"Alright," Madame Pomfrey began as she walked over carrying some small tools and a few glass tubes on a tray, some of which had liquids, "what exactly happened?"

Harry looked over at Hermione, who lightly hit his arm and gave him a stern look, he sighed and began talking.

"I woke up on the day before the second task and my teeth were like this."

She tutted, "and you didn't come to me then, why?"

He shrugged, "thought it was a prank."

She sat next to him and pulled one of his hands up, pulling a pair of nail clippers off of the tray, gesturing for him to continue, she began clipping some of the claws down as far as she could safely trim them without harming him.

"I woke up and my nails were like this the day after the task."

She hummed, dropping three claws into three separate tubes, two with liquids and one without, quickly stoppering them all.

He looked at her with a raised eyebrow, and she began to explain what she was doing with the trimmed claws.

"This one will tell us if it's mild, something like a prank or a recoverable illness like dragon pox," she said, pointing at the blue liquid, "if it's not, this one will let us know how dangerous it will be for you," this time she pointed at the red liquid.

"What about the one with no liquid?" Ron asked her.

"If it's not mild I'll need a sample to send off to researchers at St Mungo's to see if they can't find something to either help or cure the condition," she informed them.

She grabbed a metal object that looked like a tiny hook and gestured for him to open his mouth, where she began to scrape it between his teeth.

"That's a plaque scrapper," Hermione informed Ron, "it's normally used to remove hardened plaque."

Madame Pomfrey smiled, "it is, in this case, we're going to be checking his plaque to see if there are any differences in how it's built up as opposed to normal teeth," she looked at the two, as she pulled it out of his mouth, wiping the plaque off of the hook with a tiny cloth and pushing it into another tube with a purple liquid, stoppering it once she was done.

A swab was pulled out, and Harry who had been rubbing at his jaw opened his mouth once again as she pushed it into his mouth, gathering saliva.

"I'm surprised, not many people know what a plaque scrapper is," she admitted to the younger girl.

Hermione blushed, "my parents are dentists."

Madame Pomfrey smiled, "that would explain it."

She pulled the swab out of his mouth and set it into a tube with a bubbling green liquid, once again putting a stopper on it.

"What's that one for?" Harry asked, once his jaw had stopped aching.

"Checking to see if your saliva has been altered in any way, in case it could cause issues with other students should you say, catch the snitch in your mouth again."

Harry blushed and looked at his hands in embarrassment.

She hummed and checked the time on a watch on her wrist, "they should be ready in about half an hour, I suggest one of you do some of your homework as you wait."

The following half an hour felt like an eternity to Harry, anxiety bubbling in his chest.

When Madame Pomfrey returned, she checked them in reverse order.

"Your saliva seems to match up with saliva found in short furred cats, so you'll have to be careful around people with cat allergies," she informed him, moving onto the next tube, "the composition of your plaque however is normal."

They waited in tense silence as she looked over the next two tubes, comparing them with each other, before finally sighing.

"Do you want the good news or the bad news?"

Harry gulped, "the bad?"

"It appears to be a systemic virus located in your DNA; you're going to have this for the rest of your life."

His stomach dropped and he felt tears pooling in his eyes, "and the good news?"

"It's not deadly."

He nodded sadly, vaguely noticing that Hermione and Ron had both grabbed one of his hands each in support, "do you know what I should expect?"

"From the looks of things, I would think a slow transformation into a feline of some sort, however," she paused and looked him over, "from the way your claws grew in I would have to say it's a humanoid species."

"I-" he swallowed, feeling the tears fall down his face.

There was a vial being pressed up to his mouth and he drank the potion that he was being given, feeling himself calm slightly once he did.

"I've just given him a calming draught to help combat the shock," he heard Madame Pomfrey explaining to his friends, "it's not every day that you find out you have a life-changing illness."

_**What A CATastrophe** _

No new symptoms revealed themselves until the day before the third task, where Harry found himself far more agile than he had been the previous day, landing on his feet after rolling off the bed, being able to run a lot quicker than anyone, and able to jump high enough to reach the wooden rafters in the hallway.

Harry followed after Hermione and Ron on the rafters, as they made their way to the infirmary to inform Madame Pomfrey of the newest development.

"Harry, don't you think you should get down from there?" Hermione called up to him, worried.

"It's not like I'll hurt myself if I fall," he reminded her.

She huffed, hitting Ron's arm as he chuckled, "just because you can land on your feet now doesn't mean you should put yourself in danger."

Harry shrugged, jumping down as the Infirmary came into view.

"Off to my doom!" he called out as he raced off in front of them, leaving the two to catch up.

"Harry!" they both cried out at the same time, running to catch up to their increasingly fast friend.

_**What A CATastrophe** _

A week later, Harry stumbled into the common room, sitting next to Hermione in front of the fire and pulling a book off of the nearby table.

Hermione frowned, he hadn't come down in a mild panic or extremely tense as he typically did when a new symptom revealed itself, which lead her to the conclusion that he hadn't noticed the development.

"Harry," she started, waiting until he was looking at her.

"Yes, Hermione?"

"Have you, uh, looked in a mirror today?"

He frowned, "no, why?"

She reached down into the bag she had set next to her chair, and pulled out a little handheld mirror, passing it to him once he'd set the book down in his lap.

He looked into the little mirror and stared.

His eyes which had previously been his mother's green were now a vibrant honey-yellow, with slits for pupils.

The mirror slipped from his hands and landed on the floor with a soft thud, tears of both frustration and sadness filling his eyes.

"They were my mothers," he whispered, as Hermione slid over to his chair and pulled him into a hug, "and now they're gone."

_**What A CATastrophe** _

It was a week before the end of the year, and instead of excitedly pondering about their holidays of the new school year, Harry, Hermione, and Ron were all sat in Madame Pomfrey's office, Professors Dumbledore, and McGonagall, one of the researchers from St Mungos, and an older man called Newt Scamander, all crowded inside.

Harry's forearms were covered in short yellow fur with small black spots scattered across them.

Spell after spell was being cast on him, as he played chess with Ron while Hermione nervously rambled on at him.

"I'm sure you'll like it at this sanctuary they've found," she told him, and he could hear how she was holding back her tears, "I've heard that he has a way to make sure that you get a perfectly suited environment for your needs, like..." she swallowed, "like the Savannah."

Hermione had been the one to figure out just what type of feline he seemed to take after, the spots and his speed having been a dead giveaway to her.

"We'll make sure to visit," Ron told him, as he put him into a checkmate.

"We'll bring any new friends and family that we get to meet you, of course," Hermione agreed.

They politely didn't bring up the fact that the next time they saw him he just might not remember them.

_**What A CATastrophe** _

"Come on, Doctor," Hermione called, pulling him out of the TARDIS as they headed into the Burrow.

He huffed, smiling as he locked the door before they headed up.

"I'm back!" she called out to the house, a small swarm of red-headed children colliding into her legs.

"Let go of your aunt and grab your bags you little heathens," Ginny called as she walked over to her multiple nieces and nephews.

They pouted at her but did as they were told, shuffling to grab their backpacks.

"Thanks, Ginny."

"Not a problem," she grinned, then groaned as two of the boys got into an argument over who's bag was who's.

"Alright you lot," Ron called, "quickly or you won't be going."

"You still haven't told me where you're taking me," the Doctor informed Hermione.

She gave him a grin, "you've taken me to see some wonderful places, Doctor, now I get to choose where we go, and as I said, I know just the place."

"And we're going with your family because?"

Her grin became sad, "it's a place that we always go together."

He blinked, "and you trust me enough to come with you?"

"Of course, you're my friend."

"Alright," Ron said, walking over with a large rope, "everyone grab on."

The Doctor loosely grabbed the rope and Hermione turned to him, "tight, Doctor, you don't want to accidentally let go mid transport."

He frowned, but did as he was told before he felt a tugging sensation in his stomach, then felt as though he were being dragged along with the wind at such high speeds.

They landed hard, and the Doctor noticed that the weather was far warmer than it had been, and he frowned.

"America?"

"Welcome to the Scamander Reserve, Doctor."

He looked up at the building, it was old fashioned and had ivy crawling up its brickwork, he noticed that there seemed to be many metallic domes scattered around the surrounding lands.

A man walked out of the building and came up to the group with a large smile on his face, "Hello Hermione, Weasleys- Charlie couldn't make it today?"

They shook their heads, the children replying with a collective "no."

"And I don't think I've met you," he walked over to the Doctor, reaching his hand out, "Rolf Scamander."

"The Doctor," he introduced himself, shaking the offered hand.

"Right then," he clapped his hands together, "let's go see some of the creatures on the lands before we go and visit your uncle Harry, yeah?"

"Yeah!" the children cried out.

The Doctor raised an eyebrow at Hermione at the 'uncle Harry' remark, but she just shook her head and gave him a sad smile.

"What do you want to see first?"

"The Dodos!" one girl cried out.

"No way, I want to see the dragons!"

"You see dragons every day, Jamie!"

"Unicorns!"

"Unicorns are for girls!"

"I am a girl!"

The Doctor smiled at the bickering children as the man lead them all to one of the domes.

"You're going to love Wizarding Space, Doctor," Hermione informed him, with a gentle elbow to the ribs.

He frowned at her in confusion for a moment before the doors to the dome were opened and they were all ushered inside.

He gaped, "it's bigger on the inside!" then paused to frown.

Hermione gave him a rather shit-eating grin.

"I'm not supposed to be the one to say that," he protested as she laughed at him.

He looked around the rainforest that they had found themselves in and smiled, letting himself enjoy the experience.

They went from dome to dome, visiting all kinds of magical creatures, a Niffler had attempted to steal his sonic screwdriver from his pocket, but Rolf had managed to stop it in time.

They made their way back to the house at around midday.

"Lunch first, then we can visit your uncle," the man informed them as he took them to a dining room, where they all sat around a table and pulled out lunches from their bags, or in the case of Hermione and the Doctor, Ginny's bag.

Rolf went off somewhere while they were eating and came back ten minutes later with a bucket that held a leg of raw mutton inside.

"Right then," he called once he realised that they were all finished, "who's ready to see Harry?"

"Yeah!" the children cried out in excitement.

Hermione, Ron, and Ginny all looked sad, and he supposed that he was about to find out why, as they finally walked up to another dome.

Unlike the other domes, this one was small, about the size of a shed.

Inside there was a much smaller biome than the rest of the biomes, about the size of a small town if he had any guesses, it was very much a savannah, however, with quite a few trees and an oasis in the distance.

Multiple rocky outcroppings were visible from where he stood, a few of which had small cave-like shelters.

He frowned slightly, and then Rolf started talking.

"Now, who remembers where your uncle likes to nap during the day?"

"Oh, oh! Me! Me!" one of the girls called out, bouncing in place with her hand in the air.

"Yes, Julia?"

"July," she corrected, with a pout, before pointing at a tree, "he likes sleeping up there."

The Doctor looked to where she was pointing and realised that there was a Cheetah in the tree, lazily flicking its tail back and forth as it stared at them.

On a second glance, it was glaringly obvious that he was a Cheetah Person and not a normal Earth Cheetah.

"That's right, let's see if we can get him to come over, yeah?"

"Yeah!"

The Cheetah Person lifted his head as Rolf began making 'pspsps' noises before he gave a jaw cracking yawn then chirped at them.

Ron gave a grin at the noise, "he always hated that sound."

Hermione rolled her eyes at him, "your constant teasing didn't help."

He shrugged, and some happy squeals caught their attention again.

Harry had come over and was sniffing the children.

One of the younger girls reached out and began petting behind the rounded cat ears on top of his head, just behind the black hair that had managed to remain, something that he obviously enjoyed if the purring was any indication.

The Doctor frowned as he looked at him, there was no way for him to have caught that virus, as there was no way for him to have possibly gotten to the Cheetah Planet to be infected with the virus, it was also non-catching, and couldn't be inherited through DNA, so how?

His eyes caught sight of a pocket watch hanging from a chain around his neck.

It felt as though the world had been ripped out from under him as the situation made sense.

The Cheetah virus could lay dormant after treatment but could never be removed from anyone's DNA once they had it, a Time Lord's DNA could keep the worst of it from affecting them. If a Time Lord went under a Chameleon Arch after contracting the virus, they would be removing their protection from its effects, and the Cheetah virus typically re-emerged during times of stress.

The Master had gone under a Chameleon Arch, and his human self had become so stressed that the Cheetah virus took over.

"Oh Rassilon," he whispered, slowly walking over to him.

His ears twitched as he heard his approach and he turned to look at the Doctor, who sat on the ground once he'd gotten within an arm's reach of him.

The Master's ex-human self, Harry, walked over to him and began sniffing at him, his breath coming out in small puffs next to his ear.

Apparently, he decided that he liked him and thus decided that his lap was a great place to lounge on.

Rolf chuckled, "looks like you've got yourself a friend there."

The Doctor stared at him with a deadpan expression on his face, "you have no idea."

He looked at the children who were now crowded around him as they all pet Harry, who's purrs felt like he had some kind of massaging blanket on his lap, and then turned to look at Hermione.

"I think we need to talk," he looked at the other two adults, "in private," he then looked at the man on his lap and sighed, "and I doubt I'll be moving any time soon."

Hermione frowned, but looked over at Rolf, "do you think that you would be able to look after the kids for a bit?"

"Of course," he smiled, calling them over to him, ignoring their protests.

They waited until he was out of the dome and then turned to the Doctor.

"What's wrong?" Hermione asked, feeling a strange sense of Deja vu.

"This," the Doctor lifted Harry's watch for her to see, "is a Chameleon Arch."

The three frowned in confusion, sitting on the ground near the Doctor as they realised the conversation might be a long one.

"And what's that do?" Ron asked.

"Stores everything that makes a Time Lord a, well, Time Lord," he paused, carding his fingers through Harry's hair, "our DNA, memories, regeneration energy..." he trailed off in thought for a moment, "the ability to repress certain viruses and illnesses, all taken from your body and stored in a little pocket watch, leaving you whatever species you chose to hide as."

Hermione frowned, "are you saying that Harry..."

"The Cheetah virus isn't contagious, the only way it can be caught is to go to the Cheetah Planet and get infected with it there."

The only sound for a few moments was Harry's purring as the Doctor's hands found the best spots for petting.

"He was my best friend," he murmured, "and my worst enemy."

He bent down and kissed his forehead, "I loved him," he admitted to the three who were sat around him, "still do, I suppose."

"Do you," Ron started, staring at Harry, "do you know a way to sort this out then?"

The Doctor frowned at the three people who looked at him with such hope in their eyes, "I might know a way," he admitted, "but it would take multiple years for his DNA to be back where it was, and he would never be 'Harry' again," he looked down at him again, "even then, it would all rely on him opening that watch by himself."

"But you can try though, can't you?" Hermione asked him.

"For him?" he swallowed, choking back tears as the state that he'd discovered the Master in truly sunk in, "always."

**Author's Note:**

> Late one shot for the challenge because I was writing the next chapter of Show Me The Way Home and got a little bit carried away, and oh, what do you know, it's 4am and I still haven't written the one shot WHOOPS.


End file.
